This study was undertaken to evaluate an animal model for maintaining long-term patency of the ductus arteriosus. The adventitia of the ductus arteriosus of newborn lambs was infiltrated with either glutaraldehyde or formalin to maintain patency after prostaglandin E1 was infused to reopen the ductus which was assumed to be functionally closed in the first few hours after birth. The lambs were then studied at various time intervals both with hemodynamic measurements and radiographically for determination of ductus patency.